In recent years attention has been given to development of high clearance agricultural vehicles which move across the ground without damage to the agricultural products. These requirements have led to the development of vehicles that include relatively large ground wheels and raised axles so that the vehicle can pass over a top of a crop when partly or fully grown. In order to enable the vehicle to move across the ground at relatively high speed, suspension systems are necessary between the ground wheels and the axle to allow suspension movement of the ground wheels and to accommodate changes in ground level. In addition, it is necessary for the spacing between the ground wheels to be adjustable to allow the ground wheels to pass between the rows of crop and to accommodate different spacing of the row. These requirements have required special developments in the suspension systems and various techniques have been developed to overcome these problems.
One conventional agricultural vehicle suspension system utilizes tall drop boxes. The tall drop boxes transfer torque from a drive shaft, which is positioned relatively high from the ground, to a wheel hub. The tall drop boxes pivot about a pivot pin displaced from the drive shaft. Structural members above the vehicle wheels support the pivot pin. As the drive shaft connection is displaced from the pivot location the drive shaft connection is swung through an arc during articulation of the suspension. As such, relatively high suspension loads are applied directly to the pivot pin. The drive input is relatively complicated as it must accommodate the arcuate movement when the suspension is exercised. In addition, as the tall drop boxes span the height of the wheels, the wheel height is inherently limited by the drop box height.
Accordingly, it is desirable to provide a suspension system for an agricultural vehicle that provides high ground clearance, minimizes drive connection complexity and reduces high moments on the suspension system components.